Process for olefin production by metathesis and reactor system therefor

Abstract

The present invention relates to a process for obtaining an olefin by metathesis including the steps of i) feeding at least one stream with at least one olefin as starting material to at least one first reactor with at least one pre-bed having at least one compound selected from the group of alkaline earth oxides and ii) feeding the stream leaving the at least one first reactor to at least one second reactor downstream to the at least one first reactor including at least one main bed having a) at least one first catalyst component and b) at least one second catalyst component. The first and second catalyst are physically mixed with each other. The operational temperature of the at least one first reactor is lower than the operational temperature of the at least one second reactor.

The invention claimed is: 
     
       1. A process for obtaining propene by metathesis comprising the steps of
 feeding at least one stream comprising ethene and 2-butene, wherein 2-butene is supplied as a technical 2-butene stream containing 1 butene, as starting material to at least one first reactor with at least one pre-bed comprising at least one compound selected from the group consisting of alkaline earth metal oxides, wherein the at least one first reactor is operated at an operational temperature T1, and 
 feeding at least one stream leaving the at least one first reactor to at least one second reactor downstream of and separate from the at least one first reactor comprising at least one main bed comprising 
 a) at least one first catalyst component comprising a metathesis catalyst, and 
 b) at least one second catalyst component comprising an isomerisation catalyst for double bond isomerisation, wherein the at least one first catalyst and the at least one second catalyst are physically mixed with each other, 
 wherein the at least one second reactor is operated at an operational temperature T2, 
 wherein 
 the operational temperature T1 of the at least one first reactor is in a range between 150° C. and 280° C. and the operational temperature T2 of the at least one second reactor is in a range between 290° C. and 350° C., and 
 wherein the operational temperature T1 of the at least one first reactor is at least 40° C. lower than the operational temperature T2 of the at least one second reactor. 
 
     
     
       2. The process according to  claim 1 , wherein the operational temperature T1 of the at least one first reactor is in a range between 200° C. and 280° C. 
     
     
       3. The process according to  claim 1 , wherein the operational temperature T2 of the at least one second reactor is in a range between 290° C. and 330° C. 
     
     
       4. The process according to  claim 1 , wherein a stream comprising one first olefin is fed to the at least one first reactor, is mixed with at least one third olefin after leaving the at least one first reactor forming a mixture of the effluent resulted from the at least one first reactor and the at least one third olefin which is subsequently fed to the at least one second reactor. 
     
     
       5. The process according to  claim 1 , wherein a stream comprising at least two olefins as starting materials for metathesis is fed into the at least one first reactor and subsequently after leaving the at least one first reactor is fed to the at least one second reactor. 
     
     
       6. The process according to  claim 1 , wherein a pressure in the at least one first reactor and the at least one second reactor is between 1 to 50 bar. 
     
     
       7. The process according to  claim 1 , wherein a pressure in the at least one first reactor is higher or equal to a pressure in the at least one second reactor. 
     
     
       8. The process according to  claim 1 , wherein a mass ratio of the at least one pre-bed in the at least one first reactor and the at least one main bed in the at least one second reactor is between 1:10 and 3:1. 
     
     
       9. The process according to  claim 1 , wherein the at least one main bed comprises the isomerisation catalyst and the metathesis catalyst component in a mass ratio of the isomerization catalyst to the metathesis catalyst between 5:1 and 1:1. 
     
     
       10. The process according to  claim 1 , wherein the metathesis catalyst comprises oxides of metals of the Group VIB and VIIB of the Periodic Table of Elements (PSE) deposited on at least one inorganic carrier and the at least one second catalyst component comprises oxides of metals of the Group IIA of the Periodic Table of Elements. 
     
     
       11. The process according to  claim 1 , wherein the at least one pre-bed comprises an oxide selected from the group consisting of magnesium oxide, calcium oxide, strontium oxide, barium oxide or mixtures thereof. 
     
     
       12. The process according to  claim 1 , wherein a metathesis reaction is performed in the at least one second reactor at a Weight Hourly Space Velocity (WHSV) in a range between 1 and 100 h −1 . 
     
     
       13. The process according to  claim 1 , wherein the operational temperature T1 of the at least one first reactor is at least 100° C. lower than the operational temperature T2 of the at least one second reactor. 
     
     
       14. The process according to  claim 10 , wherein the metathesis catalyst comprises oxides selected from the group consisting of tungsten oxide, molybdenum oxide, or a precursor thereof. 
     
     
       15. The process according to  claim 10 , wherein the at least one second catalyst component comprises oxides of metals of the Group IIA of the Periodic Table of Elements selected from the group consisting of magnesium oxide, calcium oxide, barium oxide, strontium oxide, or mixtures thereof. 
     
     
       16. The process according to  claim 3 , wherein the operational temperature T2 of the at least one second reactor is in a range between 290° C. and 310° C. 
     
     
       17. The process according to  claim 6 , wherein the pressure in the at least one first reactor and the at least one second reactor is between 10 to 30 bar.